Aviation industry provides the only transportation networks across the globe and is thus the only dependable business for global business development and tourism. Air transportation is one of the crucial services that offer commendable social and economic benefits to a country. It provides jobs and increase tax revenue. Air transportation is evidently the fastest mechanism for movement of peopled and cargo shipments across the world. In terms of social factors, air transport broadens people’s leisure and cultural experiences. It provides a cheaper and efficient platform for talking holiday vacations and visiting distant friends and family.
Automobiles all over the world have been seeking ways of controlling and managing fuel consumption in airlines due to the biting economical conditions exacerbated by pinching gas pumps prices. The number of airline companies in the world is approximated to reach 1000 with a fleet of more than 22,000 aircrafts. The airlines transport nearly 2 billion passenger annually and 40% of interregional cargo. An estimated 2 million people are directly or indirectly employed by the airlines in form of crews, maintenance staff and handling agents.
In order for airlines to perform effectively in a competitive environment that only provides marginal profits, it needs efficient decision making and management practices that optimize technology and reduce costs. Airlines use tactics based on scientific and mathematical methods to arrive at conclusions favorable for cost minimization and profit maximization.
Fuel management programs are among the processes undergone by airlines to reduce consumption and overall cost. This is executed in form of fuel minimization programs that involve maintenance, flight operation procedures, and fleet programs.
Airlines have implemented programs and technologies that are aimed at improving environmental performance around the world and fuel consumption. The programs are significantly intended to reduce fuel consumption and emission of pollutant gases thus saving the company millions of dollars on fuel bills yearly. The innovative programs adopted by some airlines demonstrate the importance of environmental concerns as core fundamentals in daily practices and engineering processes in addition to cost reduction.
Maintenance practices
Maintenance refers to the practice of keeping the aircraft in the best possible condition to minimize wear and tear and improve performance. In order to reduce unnecessary fuel weight, the flight must be planned very correctly to calculate the exact fuel quantity to be embarked. Flight planning is done basing on aircraft maintenance monitoring by incorporating performance factors derived from specific range variations.
- Weight reduction
Removing unnecessary equipments in the aircraft and minimizing unnecessary uplifting makes a big difference in terms of fuel savings. Portable water tanks carry water to a capacity of 60 US gallons. Limiting the amount of water carried in the aircraft through installation of amount indicators ensures that only the correct amount is carried. Also route specific surveys details the act amount of water needed for a given route.
Using light weight galley carts reduces unnecessary weight on the aircraft. Galley carts are used by crew onboard to serve food. Lightweight carpets of up to 880g/Sqm can be used instead of the standard 1600g/Sqm. It provides the same strength and durability.
- Aerodynamic cleanliness
Aircraft aerodynamics deal with the drag of an aircraft at a given velocity and weight. Induced drag and parasite drag are the two variables used to analyze changes. Given a given weight, air density and velocity, induced drag is a function of span. An increased span leads to reduction in fuel per mile as time per mile increases. Induced drag is greatest at low speeds and vice versa. This implies that the impact of reduction in induced drag increases as induced drag is increased – at low speeds.
Parasite drag is a function of how aerodynamically clean an aircraft is and of the wing area. Reduction in fuel due to reduced parasite drag is greatest at high speeds (low time per mile) where parasite drag is low.
Wing fences consist of vertical fins that are attached to the upper wing surface to reduce out-flow of air over the upper camber thereby reducing inducing drag. Winglets, on the other hand are vertical wing-like components that have been attached to the wingtips to serve as inhibitors to development of wingtip vortices and reduce induced drag.
Vortex generators have found the way into the leading edge of an air foil. Vortex generators are small fins or air foils placed perpendicular to the upper wing surface. They are placed to meet the laminar flow originating from over the wing as a result of slight angle attack. They are used to generate vortices which regenerate the boundary layer and delay turbulent flow lowering resistance.
- Cruise performance monitoring
In case of excessive fuel flow or drag increment detected through performance monitoring, proper investigation should be conducted to ascertain the causes. Consequently, appropriate action should be taken through proper maintenance corrective actions. This may include surface cleaning, engine wash and clean up, engine repair, aerodynamic cleanness and weight reduction. Aircraft performance is measured by FOS Cruise Performance Monitoring tools that give insight to aircraft analytics indicating engine performance degradation or fuselage drag. CPM modules enable the comparison of aircraft performance, mainly torque, fuel flow and IAS with the theoretical values computed by the Flight Operation System. For aircraft fitted with Multi Purpose Computer (MPC), the details are automatically recorded during the stabilized cruise phase and transmitted to the PCMCIA card of the MPC for storage. Analysis of the by the crew reveal important analytics concerning engine performance and degradation.
- Engine maintenance
Research has shown that an enhanced relationship between the maintenance crew and pilots is beneficial for general engine durability. Proper engine handling procedures minimizes the maximum or sustained engine temperatures towards increased hot section life. Some airlines have implemented yearly trainings/meetings and awareness programs with pilots to increase collaboration.
It is normal for engines just like any other mechanical objects to experience rubbing, thermal stress, dirt accumulation, foreign object ingestion, and mechanical stress. These effects eventually degrade the performance of the engine. The interturbine temperature increases under such conditions decreasing engine efficiency and power. Fuel consumption is incremented to attain a given power. Thus, it is important to monitor ITT at take off and correct any defects as soon as possible.
Another factor that can be used to determine engine efficiency is Specific Fuel Consumption. SFC increases as engine performance decreases and exhibit a direct effect on aircraft performance in form of Specific range and increased fuel burn.
It is important to balance the degradation of parameters and consequent effects of fuel consumption against costs associated with complete v engine overhaul. Engine overhaul may be postponed through careful maintenance while it remains on wing.
Flight operations management
The following procedures describe the best practices for fuel economy.
- Auxiliary Power Unit
The APU burns jet fuel to power aircraft systems, light the cabin and warm or cool the air inside the aircraft as needed. Using the available ground power and preconditioned air equipment rather than the APU saves gallons of fuel to the tune of 6 million and reduces CO2 emission by 126 million pounds.
- Hotel mode
Aircrafts standing at the ramp consume up to 110kg/hour of fuel for PW127 engine. If airport facilities allow, the use of GSU to give the required power supply on ground is economical.
- Taxiing
Good estimates of taxiing times should be implemented and standards estimates varied as necessary. All aircrafts spend a considerable time on the ground taxiing from the terminal to the runaway and back. In order to combat fuel wastage, the fli9ght crew should choose to reach and leave the runaway from intermediate taxiways when the entire runaway is not necessary.
- Climb
Speed laws dictates that the higher the speed, the lower the climb path, and the more time spent at low flight level, the longer the climb and the more the fuel is used. According to FCOM, climb speeds of 170kts and 190kts are recommended. The difference in fuel consumption between the two speeds to a fixed cruise level is considerable. Thus, a the computed fuel economy level difference between the two speeds for a ATR 72-500 accounts up to 26% . This amount could make a cost difference.
Fig. 1 Fuel consumption difference between 170kts and 190kts speed for a typical ATR 72- 500.
Fleet programs
A quality flight planning system is essential for achieving optimized fuel economy and reduction of operating costs. A good flight planning system will optimize routes in terms of tracks, speeds, altitudes, weight, payload and the state of the aircraft.
An aircraft used for a certain route is determined by numerous factors. Among them include passenger traffic, environmental conditions and safety. A route is determined by economical sensibility. Airbus A32, for instance, as the largest fuselage member cannot be chosen for use in a route with reduced passenger traffic when the 100-seater A318 could be economical. Likewise, technological aspects dictate the type of aircraft. It does not make sense to use A320 on a non-stop transpacific route. A340 could be more reasonable to use for long hauls.
Fig. 2 Effectiveness of Airbus A318 versus A320 on short routes
According to airline regulatory authorities, there are stipulated period and conditions that an aircraft is allowed to operate in a certain routed. These terms and conditions should be kept strictly to achieve the best out of aircrafts and reduce fuel costs. By applying cost indexing, the fuel burn per trip time is determined and offset with time related costs such as hourly maintenance cost, flight and cabin crew cost, marginal depreciation and leasing costs. The cost of fuel is compared with the cost of time and determination of cost index done according to each specific airline and situation.
Other factors such as wind forecasting and centre of gravity position should determine the fleet program for optimized fuel consumption. Winds have significant influence on fuel consumption and it is significant to determine the meteorological conditions before flight. Cruise altitude, optimum altitude and specific range determine the favorable cruise altitude for optimum fuel consumption. The centre of gravity of the aircraft payload and fuel should always be kept at its operational envelope. It is recommended to have the centre of gravity as far aft as possible for maximum fuel saving.
References
Bazargan, M. (2010). Airline Operations and Scheduling. Ashgate Publishing, Ltd.
Council, N. R. (2010). Policy Options for Reducing Energy Use and Greenhouse Gas Emissions from U.S. Transportation. Transportation Research Board.
Goglia, J. J. (2012). Implementing Safety Management Systems in Aviation. Ashgate Publishing, Ltd.
King, F. H. (1980). Aviation Maintenance Management. SIU PRESS.
Konstantinos Zografos, G. A. (2013). Modelling and Managing Airport Performance. John Wiley & Sons.
